CHARACTERIZATION, ANALYSIS, AND TESTING Flashcards
analytical branch of polymer science
➢Polymer characterization
➢Polymer characterization is a technique used to determine the
molecular properties, structure, and behavior of polymers.
The information obtained from polymer characterization can also be
used for
process control and product quality assessment
Characterization techniques are typically used to
determine
molecular mass
molecular structure
morphology
thermal properties
mechanical properties
Extremely large molecular weights are observed in polymers with
very long chains
The molecular mass of a polymer _______ from typical molecules
differs
t polymerization reactions produce a _________ of molecular
weights and shapes.
distribution
During the polymerization process, ______ polymer chains will grow to
the same length
not all
resulted in the different lengths in the growing part of the polymerization
distribution of chain lengths or
molecular weights.
The distribution of molecular masses can be summarized by
number average molecular weight
weight average molecular weight
polydispersity.
common methods for determining number average molecular weight,
weight average molecular weight and
polydispersity
parameters
colligative property measurements
static light
scattering techniques
viscometry
size exclusion chromatography
There are four molecular weight
averages in common use
number-average molecular weight, Mn
the weight-average molecular weight, Mw
the z-average molecular weight, Mz
viscosity-average molecular weight, Mv
highest to lowest
Mn < Mv < Mw < Mz
equation for Number-Average Molecular Weight, Mn
(image 5 & 6)
Determination of
Molecular Weight (physical and chemical methods)
- end group analysis
- measurement of colligative properties
- light scattering
- Ultracentrifugation
- dilute solution viscosity
- gel permeation chromatography (GPC).
equation of Number-Average Degree of Polymerization, DPn
(image 7)
equation of Weight-Average Molecular Weight
(image 8 &9)
if all species in a polymer sample have the same molecular weight
𝑀𝑛 = 𝑀𝑤 = 𝑀z
If all species in a polymer sample have the same molecular weight (that
is, the polymer is ____________)
monodisperse
ratio Mw/Mn
polydispersity index (PDI)
as a simple measure of the polydispersity of the polymer sample
polydispersity index (PDI)
a chemical method use for calculating the number-average molecular weight of polymer samples whose molecules contain reactive functional groups at one end or both ends of the molecule.
- End-group Analysis
This method is limited to the determination of polymers with a molecular weight of less than about 20,000.
- End-group Analysis
method of analysis in an end-group Analysis
✓Titrimetric method
✓Nuclear magnetic resonance (NMR)
✓mass spectrometry
✓vibrational spectrometry, like infrared and raman spectroscopy.